Image processing apparatus and image forming apparatus

ABSTRACT

According to one embodiment, there is provided an image processing apparatus including a reading unit and a determining unit. The reading unit generates sheet image data indicating image data of a sheet. The determining unit determines, on the basis of a degree of gradation in the sheet image data generated by the reading unit, whether a planar object adheres on the sheet read by the reading unit.

FIELD

Embodiments described herein relate generally to an image processingapparatus and an image forming apparatus.

BACKGROUND

There is known a technique for reading an image formed on a sheet-likemedium (hereinafter referred to as “sheet”) such as paper. On the otherhand, a planar object such as a label is sometimes stuck to the sheet.If the planar object is stuck to the sheet, in the related art, thesheet to which the object is stuck and a sheet to which the object isnot stuck sometimes cannot be distinguished.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of the external appearance of animage forming apparatus including an image processing apparatus in afirst embodiment;

FIG. 2 is a diagram for explaining an example of the configuration ofthe image forming apparatus centering on an image reading unit;

FIG. 3 is a diagram showing an example of the functional configurationof the image forming apparatus including the image processing apparatusin the first embodiment;

FIG. 4 is a diagram for explaining a control method for an image-readingcontrol unit;

FIG. 5 is a diagram showing a state of the surface of a sheet withrespect to a control result of the image reading unit by theimage-reading control unit;

FIG. 6 is a diagram showing a state in reading the sheet on apredetermined conveying route;

FIG. 7 is a diagram showing sheet image data obtained by representingpixels in binary values as a processing result of an extracting unit;

FIG. 8 is a flowchart for explaining an example of a flow of a partialoperation of the image processing apparatus in the first embodiment;

FIG. 9 is a flowchart for explaining an example of a flow of a partialoperation of the image processing apparatus in the first embodiment;

FIG. 10 is a flowchart for explaining an example of a flow of a partialoperation of an image processing apparatus in a second embodiment; and

FIG. 11 is a flowchart for explaining an example of a flow of a partialoperation of the image processing apparatus in the second embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided an imageprocessing apparatus including a reading unit and a determining unit.The reading unit generates sheet image data indicating image data of asheet. The determining unit determines, on the basis of a degree ofgradation in the sheet image data generated by the reading unit, whethera planar object adheres on the sheet read by the reading unit.

Exemplary embodiments are explained below with reference to thedrawings.

FIG. 1 is a diagram showing an example of the external appearance of animage forming apparatus 1 including an image processing apparatus 100 ina first embodiment.

The image forming apparatus 1 is a multifunction printer (MFP) that canform an image on a sheet S. For example, the image forming apparatus 1has a print function, a copy function, a scan function, or a facsimilefunction. For example, the sheet S is paper on which an originaldocument, characters, pictures, and the like can be formed. The sheet Smay be any object as long as the image forming apparatus 1 can form animage on the object.

The image forming apparatus 1 includes an image reading unit 10, acontrol panel 30, an image forming unit 40, and an image processingapparatus 100. Note that the image reading unit 10 is an example of a“reading unit”.

The image reading unit 10 reads an image from a sheet placed in apredetermined position. For example, the image reading unit 10 includesan image pickup device such as a CCD or a CIS. The CCD is anabbreviation of “Charge Coupled Device”. The CIS is an abbreviation of“Contact Image Sensor”. The image reading unit 10 generates image datafrom the read image and outputs the generated image data to the imageprocessing apparatus 100. In the following explanation, the image datagenerated by the image reading unit 10 is described as “sheet imagedata”. Note that a planar object having predetermined thickness issometimes stuck to the sheet S in this embodiment. In the followingexplanation, it is assumed that the planar object having thepredetermined thickness is stuck to the sheet S. In the followingexplanation, the planar object having the predetermined thickness isdescribed as “label R”.

The control panel 30 functions as a user interface that receives anoperation input from a user. The control panel 30 includes, for example,a touch panel in which an operation unit and a display unit areintegrally formed. The control panel 30 is communicably connected to theimage processing apparatus 100. For example, the operation unit of thecontrol panel 30 receives an instruction for the operation of the imageforming apparatus 1. For example, the instruction for the operationincludes an instruction for a scan function for performing reading of animage. For example, the instruction for the operation includes aninstruction for a copy function for printing a predetermined image on asheet. After receiving an operation input, the control panel 30generates an operation signal based on the operation input.

The display unit of the control panel 30 displays information to theuser. For example, the display unit of the control panel 30 displays adetermination result of a determining unit 124.

The image forming unit 40 forms an image on the sheet S using a coloringagent such as toner or ink. Specifically, the image forming unit 40forms an image on the basis of the sheet image data read by the imagereading unit 10 or image data received from an external apparatus. Forexample, the image forming unit 40 forms an image on the sheet S usingan inkjet system, a laser system, or a thermal system.

The image processing apparatus 100 is a computer that applies variousimage processing to the acquired image data. The image processingapparatus 100 appropriately controls the image reading unit 10 and theimage forming unit 40.

FIG. 2 is a diagram for explaining an example of the configuration ofthe image forming apparatus 1 centering on the image reading unit 10.The image reading unit 10 includes an image pickup device 12, a lens 14,a driving mechanism 16, a driving unit 18, and a light 20. The light 20is an example of an “irradiating unit”.

A conveying unit 60 explained below drives a conveying mechanism andconveys the sheet S to a predetermined position in the image formingapparatus 1. For example, the conveying mechanism includes a pickuproller 61, a paper feeding roller 62, a separating roller 64,pre-reading rollers 66, and post-reading rollers 68.

For example, the pickup roller 61 conveys the sheets S placed one on topof another to a conveying route in order from the sheets S on the upperside (in a Y direction in the figure).

The paper feeding roller 62 conveys the sheet S conveyed by the pickuproller 61 to a conveying route on the side of the pre-reading rollers 66and the post-reading rollers 68. The separating roller 64 is arranged ina position opposed to the paper feeding roller 62. Note that anarrangement interval between the paper feeding roller 62 and theseparating roller 64 is an interval equivalent to the thickness of onesheet S. The separating roller 64 rotates in a direction opposite to arotating direction of the paper feeding roller 62. Consequently, theseparating roller 64 separates the sheet S in contact with theseparating roller 64 and one sheet S in contact with the paper feedingroller 62. As a result, even if a plurality of the sheets S overlap, itis possible to convey only one sheet S to a conveying route at a laterstage.

The driving unit 18 drives the driving mechanism 16 and adjusts thepositions of the image pickup device 12 and the lens 14. The positionindicates a position in a three-dimensional space represented by X-Y-Zin the figure. For example, the driving unit 18 is an actuator such as amotor. The driving unit 18 drives the driving mechanism 16 according toa control signal output from the image processing apparatus 100.Specifically, the driving unit 18 adjusts an optical axis of the imagepickup device 12 and the lens 14 to be located on a predeterminedconveying route. The predetermined conveying route is a section betweenthe pre-reading rollers 66 and the post-reading rollers 68. Note thatthe driving unit 18 may adjust the position of the entire image readingunit 10 including the light 20.

The lens 14 condenses, on the surface of the sheet S, reflected light oflight irradiated from the light 20. The reflected light condensed by thelens 14 is received by the image pickup device 12. As a result, theimage pickup device 12 generates sheet image data. Note that the lightcondensed by the lens 14 may include not only the reflected light of thelight irradiated from the light 20 but also other lights. For example,the other lights are sunlight, the light irradiated from the light 20,and illumination light of a room where the image forming apparatus 1 isplaced. Note that the light 20 is suitably a point light source or alight source similar to the point light source.

Summarizing the above, with the configuration of the image reading unit10, the image pickup device 12 can pick up an image of the sheet Sconveyed in a direction of an arrow V shown in the figure.

FIG. 3 is a diagram showing an example of the functional configurationof the image forming apparatus 1 including the image processingapparatus 100 in the first embodiment.

A discharging unit 50 discharges the sheet S conveyed by the conveyingunit 60 to the outside of the image forming apparatus 1. For example,the discharging unit 50 is a so-called finisher.

The image processing apparatus 100 includes a control unit 110 and astoring unit 130. The control unit 110 includes an image-reading controlunit 112, a conveyance control unit 114, an image-formation control unit116, an acquiring unit 118, an extracting unit 120, a calculating unit122, and a determining unit 124. Note that the calculating unit 122 andthe determining unit 124 are examples of a “determining unit”.

Apart or all of the functional units of the control unit 110 aresoftware functional units. The software functional units function when aprocessor executes a computer program stored in the storing unit 130.For example, the processor is a CPU (Central Processing Unit). A part orall of the functional units of the control unit 110 may be hardwarefunctional units. For example, the hardware functional unit is an LSI oran ASIC. The LSI is an abbreviation of “Large Scale Integration”. TheASIC is an abbreviation of “Application Specific Integrated Circuit”.

The image-reading control unit 112 controls the image reading unit 10.For example, the image-reading control unit 112 controls timing ofreading of the sheet S by the image reading unit 10. For example, theimage-reading control unit 112 controls a reading position of the imagereading unit 10. Specifically, the image-reading control unit 112generates a control signal for controlling the driving unit 18. Theimage-reading control unit 112 outputs the generated control signal tothe driving unit 18. Consequently, the image reading unit 10 changes theposition as appropriate on the three-dimensional space. For example, theimage-reading control unit 112 controls the light 20 in the imagereading unit 10. Specifically, the image-reading control unit 112controls the light 20 to be lit and controls the light 20 to beextinguished.

The control of the image-reading control unit 112 is explained withreference to FIGS. 4 and 5. FIG. 4 is a diagram for explaining a controlmethod for the image-reading control unit 112.

For example, the image-reading control unit 112 controls the position ofthe light 20 such that the light 20 irradiates light on the surface ofthe sheet S from a predetermined incident angle. For example, thepredetermined incident angle is approximately 60°. That is, theimage-reading control unit 112 controls the position of the light 20such that the light 20 irradiates light on the surface of the sheet Sfrom an oblique direction. Consequently, if a label R is stuck to thesurface of the sheet S, a shadow SD corresponding to the thickness ofthe label R is formed on the surface of the sheet S as a projectedimage. The image-reading control unit 112 controls the position of theimage reading unit 10 such that the shadow SD is included in a readingregion A of the image reading unit 10.

FIG. 5 is a diagram showing a state of the surface of the sheet S withrespect to a control result of the image reading unit 10 by theimage-reading control unit 112. For example, in the case of an exampleshown in FIG. 5, the image-reading control unit 112 controls the light20 to irradiate light from a downward direction to an oblique rightupward direction in the figure. In such a case, the shadow SD is formedon the surface of the sheet S to cover two sides of the label R.Consequently, edge extraction processing of the extracting unit 120explained below can be suitably performed.

FIG. 6 is a diagram showing a state in reading the sheet S on thepredetermined conveying route. For example, in the case of FIG. 6, aplurality of labels R having different sizes are stuck to the surface ofthe sheet S. The image-reading control unit 112 controls the position ofthe image reading unit 10 such that a corner of the sheet S and a partof a road surface B of the predetermined conveying route are included inthe reading region A. For example, the image-reading control unit 112controls the position of the image reading unit 10 such that the readingregion A overlaps the position at the right corner of the sheet S in thefigure.

The explanation is continued with reference to FIG. 3 again.

The conveyance control unit 114 controls the conveying unit 60. Forexample, the conveyance control unit 114 controls conveying speed of thesheet S. For example, the conveyance control unit 114 switches,according to the sheet S, the conveying route on which the sheet S isconveyed. Consequently, for example, the conveying unit 60 can conveythe sheet S read by the image reading unit 10 to the image forming unit40. In the following explanation, control for conveying the sheet S readby the image reading unit 10 to the image forming unit 40 is describedas “normal conveyance control”.

For example, the discharging unit 50 discharges the sheet S, on whichthe image is formed by the image forming unit 40, to the outside of theimage forming apparatus 1.

The image-formation control unit 116 controls the image forming unit 40.For example, the image-formation control unit 116 controls, according toa determination result of the determining unit 124, the image formingunit 40 to form an image on the sheet S. Specifically, if thedetermining unit 124 determines that the label R is stuck on the sheetS, the image-formation control unit 116 performs processing explainedbelow. The image-formation control unit 116 controls the image formingunit 40 to form an image on the label R. In this case, theimage-formation control unit 116 controls the position of a formationregion of the image on the basis of the position of the label Rcalculated by the calculating unit 122 explained below.

The acquiring unit 118 acquires sheet image data from the image readingunit 10. The acquiring unit 118 acquires an operation signal from thecontrol panel 30. The acquiring unit 118 may acquire various image datafrom an external apparatus via a not-shown interface. The acquiring unit118 causes the storing unit 130 to store the sheet image data, theoperation signal, or the image data acquired as explained above.

The extracting unit 120 extracts an edge indicating the contour of thesheet S from the sheet image data acquired by the acquiring unit 118. Inthis embodiment, the edge indicates a place where gradation ofbrightness suddenly changes in the image data. Note that the edge may bea place where a color suddenly changes. The edge indicating the contourof the sheet S includes an edge in the horizontal direction with respectto a conveying direction of the sheet S and an edge in the verticaldirection with respect to the conveying direction of the sheet S. In thefollowing explanation, the edge in the horizontal direction included inthe edge indicating the contour of the sheet S is described as“horizontal edge HE1”. The edge in the vertical direction included inthe edge indicating the contour of the sheet S is described as “verticaledge VE1”.

The extracting unit 120 extracts an edge indicating the contour of thelabel R from the sheet image data acquired by the acquiring unit 118.Like the edge indicating the contour of the sheet S, the edge indicatingthe contour of the label R includes an edge in the horizontal directionand an edge in the vertical direction with respect to the conveyingdirection of the sheet S. In the following explanation, the edge in thehorizontal direction included in the edge indicating the contour of thelabel R is described as “horizontal edge HE2”. The edge in the verticaldirection included in the edge indicating the contour of the label R isdescribed as “vertical edge VE2”. In the following explanation, thehorizontal edge HE1, the vertical edge VE1, the horizontal edge HE2, andthe vertical edge VE2 are collectively described as “edge group” if theedges are not particularly distinguished from one another.

A specific extraction method for the edge group is explained below.

The extracting unit 120 extracts a luminance value for each of pixelsconfiguring the sheet image data. In extracting the luminance value, theextracting unit 120 focuses on any pixel of the sheet image data. In thefollowing explanation, the pixel focused on by the extracting unit 120is described as “target pixel”. The extracting unit 120 calculates adifference between a luminance value of the target pixel and a luminancevalue of pixels around the target pixel. The extracting unit 120compares a value of the calculated difference and a threshold. Forexample, if the value of the calculated difference exceeds thethreshold, the extracting unit 120 allocates “1”. If the value of thecalculated difference is equal to or smaller than the threshold, theextracting unit 120 allocates “0”. That is, the extracting unit 120converts the target pixel into a binary value “1” or “0” according tothe value of the calculated difference. If a fixed number or more ofpixels that take any one value among the pixels converted into thebinary values are continuous, the extracting unit 120 joins thecontinuous pixels. The extracting unit 120 extracts the joined pixels asan edge.

For example, the extracting unit 120 extracts an edge group using aSOBEL operator as a method of calculating the difference between theluminance values. Note that the extracting unit 120 may use a PREWITToperator or other operators instead of the SOBEL operator.

The extracting unit 120 may extract an edge group using a zero-crossingmethod. For example, the extracting unit 120 secondarily differentiatesa change in the luminance values on the sheet image data. The extractingunit 120 extracts a position P1 where the secondarily-differentiatedluminance value crosses zero when the luminance value changes from apositive peak to a negative peak. The extracting unit 120 extracts aposition P2 where the secondarily-differentiated luminance value crosseszero when the luminance value changes from the negative peak to thepositive peak. The extracting unit 120 extracts the edge group usingHough transform on the basis of a pixel indicated by the extractedposition P1 and a pixel indicated by the extracted position P2.

The extracting unit 120 may smooth the luminance value of the entiresheet image data before extracting the edge group using the zero-crossmethod. For example, the extracting unit 120 applies a Gaussian filterto the sheet image data and smoothes the luminance value of the entiresheet image data. For example, the extracting unit 120 extracts the edgegroup using a Canny method as a method of performing the smoothingbeforehand. Consequently, the extracting unit 120 can remove noise whenextracting the edge group.

FIG. 7 is a diagram showing an example of sheet image data obtained byrepresenting pixels in binary values as a processing result of theextracting unit 120. For example, the extracting unit 120 convertspixels in a region on the road surface B into “0” in the sheet imagedata. For example, the extracting unit 120 converts pixels in a regionof the sheet S into “1” in the sheet image data. For example, theextracting unit 120 converts pixels in a region of the shadow SD of thelabel R into “0” in the sheet image data.

By performing the processing explained above, the extracting unit 120extracts a boundary between the sheet S and the road surface B of thepredetermined conveying route as the horizontal edge HE1 or the verticaledge VE1. The extracting unit 120 extracts a boundary between the sheetS and the label R as the horizontal edge HE2 or the vertical edge VE2.

The calculating unit 122 calculates a pixel region indicating the sizeof the sheet S in the sheet image data. For example, the calculatingunit 122 calculates a pixel region of the sheet S on the basis of theposition of the horizontal edge HE1, conveying speed, and an actual sizeof the sheet S. The conveying speed is speed in conveying the sheet S bythe conveying unit 60. The actual size of the sheet S is detected by apredetermined sensor when the sheet S is conveyed on the conveying routeof the conveying unit 60.

More specifically, the calculating unit 122 sets the horizontal edge HE1as a reference and calculates the position of the terminal end of thesheet S on the sheet image data. The position of the terminal end is aposition equivalent to the opposite side of the side indicated by thehorizontal edge HE1 if it is assumed that the sheet S has a squareshape. Consequently, the calculating unit 122 calculates a pixel regionbetween the horizontal edge HE1 and the terminal end as a pixel regionindicating the size of the sheet S. Note that the calculating unit 122may calculate the pixel region of the sheet S using the position of thevertical edge VE1. The calculating unit 122 may calculate the pixelregion of the sheet S using both the positions of the horizontal edgeHE1 and the vertical edge VE1. In this case, the calculating unit 122can more accurately calculate the pixel region of the sheet S.

The calculating unit 122 calculates, on the basis of the horizontal edgeHE2 and the vertical edge VE2, a position where the label R is stuck.For example, the calculating unit 122 forms a square on data using anintersection of both the edges HE2 and VE2 and edge lengths of both theedges HE2 and VE2. The calculating unit 122 calculates an internalregion of the square as a pixel region of the label R. The calculatingunit 122 calculates the position where the label R is stuck from apositional relation between the pixel region of the label R and thepixel region of the sheet S.

The determining unit 124 determines, on the sheet image data, whetherthe horizontal edge HE2 or the vertical edge VE2 is included in thepixel region of the sheet S. If the horizontal edge HE2 or the verticaledge VE2 is included, the determining unit 124 determines that the labelR is stuck on the sheet S. If the horizontal edge HE2 or the verticaledge VE2 is not included, the determining unit 124 determines that thelabel R is not stuck on the sheet S. In the following explanation, astate in which the label R is stuck on the sheet S is described as “thelabel R is present”. A state in which the label R is not stuck on thesheet S is described as “the label R is absent.

The storing unit 130 includes a nonvolatile storage medium and avolatile storage medium. For example, the nonvolatile storage medium isa ROM, a flash memory, or a HDD. The ROM is an abbreviation of “ReadOnly Memory”. The HDD is an abbreviation of “Hard Disk Drive”. Forexample, the volatile storage medium is a RAM or a register. The RAM isan abbreviation of “Random Access Memory”. Information stored in thestoring unit 130 includes the sheet image data, the edge group, theposition of the label R, the pixel region of the sheet S, and thedetermination result of the determining unit 124.

A flow of the operation of the image processing apparatus 100 in thefirst embodiment is explained below with reference to FIGS. 8 and 9.FIGS. 8 and 9 are flowcharts for explaining examples of flows of partialoperations of the image processing apparatus 100 in the firstembodiment. For example, the image processing apparatus 100 in thisembodiment performs processing of the flowcharts at a predeterminedcycle.

First, the image-reading control unit 112 controls the image readingunit 10 (ACT 100). Subsequently, the acquiring unit 118 acquires sheetimage data from the image reading unit 10 (ACT 102).

Subsequently, the extracting unit 120 extracts the horizontal edge HE1from the sheet image data acquired by the acquiring unit 118 (ACT 104).Subsequently, the extracting unit 120 extracts the vertical edge VE1from the sheet image data acquired by the acquiring unit 118 (ACT 106).Note that the image processing apparatus 100 may perform the action inACT 106 before the action in ACT 104.

Subsequently, the calculating unit 122 calculates a pixel region of thesheet S using both of the horizontal edge HE1 and the vertical edge VE1(ACT 108).

Subsequently, the determining unit 124 determines whether the horizontaledge HE2 is included in the pixel region of the sheet S calculated bythe calculating unit 122 (ACT 110). If the horizontal edge HE2 is notincluded (NO in ACT 110), the determining unit 124 determines that “thelabel R is absent” (ACT 112). Consequently, the image processingapparatus 100 ends the processing of the flowcharts.

If the horizontal edge HE2 is included (YES in ACT 110), the determiningunit 124 performs determination explained below. The determining unit124 determines whether the vertical edge VE2 is included in the pixelregion of the sheet S (ACT 114). If the vertical edge VE2 is notincluded (NO in ACT 114), the determining unit 124 determines that “thelabel R is absent” (ACT 112). Consequently, the image processingapparatus 100 ends the processing of the flowcharts. Note that the imageprocessing apparatus 100 may perform the action in ACT 114 before theaction in ACT 110.

If the vertical edge VE2 is included (YES in ACT 114), the determiningunit 124 determines that the label R is present (ACT 116). Thecalculating unit 122 calculates the position of the label R (ACT 118).

Subsequently, the conveyance control unit 114 controls the conveyingunit 60 with a method of normal conveyance control (ACT 120). That is,the conveyance control unit 114 controls the conveying unit 60 to conveythe sheet S read by the image reading unit 10 to the image forming unit40.

The image-formation control unit 116 controls, on the basis of theposition of the label R, the image forming unit 40 to form an image onthe label R (ACT 122). Consequently, the image processing apparatus 100ends the processing of the flowcharts.

In the image processing apparatus 100 in the first embodiment explainedabove, the image reading unit 10 reads the sheet S and generates sheetimage data. The determining unit 124 determines, on the basis of aluminance value of the sheet image data, whether a label is stuck on thesheet S, which is a reading target. As a result, the image processingapparatus 100 can distinguish a sheet to which an object is stuck and asheet to which the object is not stuck.

In the image processing apparatus 100 in the first embodiment, thecalculating unit 122 calculates the position of the label Ron the sheetimage data. Consequently, the image forming apparatus 1 can form apredetermined image in the position of the label R on the sheet S.

The image processing apparatus 100 in a second embodiment is explainedbelow. The image processing apparatus 100 in the second embodiment isdifferent from the image processing apparatus 100 in the firstembodiment in that, if the label R is stuck on the sheet S, the sheet Sis discharged to the outside of the image forming apparatus 1. Thisdifference is mainly explained. Explanation of similarities to the firstembodiment is omitted.

The conveyance control unit 114 controls, according to a determinationresult of the determining unit 124, the conveying unit 60 to convey thesheet S read by the image reading unit 10 to the discharging unit 50. Inthe following explanation, the control for conveying the sheet S read bythe image reading unit 10 to the discharging unit 50 is described as“discharge conveyance control”. Specifically, if the determining unit124 determines that the label R is stuck on the sheet S, the conveyancecontrol unit 114 performs the discharge conveyance control. If thedetermining unit 124 determines that the label R is not stuck on thesheet S, the conveyance control unit 114 performs the normal conveyancecontrol.

A flow of the operation of the image processing apparatus 100 in thesecond embodiment is explained below with reference to FIGS. 10 and 11.FIGS. 10 and 11 are flowcharts for explaining examples of flows ofpartial operations of the image processing apparatus 100 in the secondembodiment.

First, the image-reading control unit 112 controls the image readingunit 10 (ACT 200). Subsequently, the acquiring unit 118 acquires sheetimage data from the image reading unit 10 (ACT 202).

Subsequently, the extracting unit 120 extracts the horizontal edge HE1from the sheet image data acquired by the acquiring unit 118 (ACT 204).Subsequently, the extracting unit 120 extracts the vertical edge VE1from the sheet image data acquired by the acquiring unit 118 (ACT 206).Note that the image processing apparatus 100 may perform the action inACT 206 before the action in ACT 204.

Subsequently, the calculating unit 122 calculates a pixel region of thesheet S using both of the horizontal edge HE1 and the vertical edge VE1(ACT 208).

Subsequently, the determining unit 124 determines whether the horizontaledge HE2 is included in the pixel region of the sheet S calculated bythe calculating unit 122 (ACT 210). If the horizontal edge HE2 isincluded (YES in ACT 210), the determining unit 124 determines that “thelabel R is present” (ACT 212).

Subsequently, the conveyance control unit 114 controls the conveyingunit 60 with a method of discharge conveyance control (ACT 214). Thatis, the conveyance control unit 114 controls the conveying unit 60 toconvey the sheet S read by the image reading unit 10 to the dischargeunit 50. Consequently, the image processing apparatus 100 ends theprocessing of the flowcharts.

If the horizontal edge HE2 is not included (NO in ACT 210), thedetermining unit 124 determines that “the label R is absent” (ACT 216).

Subsequently, the conveyance control unit 114 controls the conveyingunit 60 with a method of normal conveyance control (ACT 218). That is,the conveyance control unit 114 controls the conveying unit 60 to conveythe sheet S read by the image reading unit 10 to the image forming unit40. Consequently, the image processing apparatus 100 ends the processingof the flowcharts.

With the image processing apparatus 100 in the second embodimentexplained above, the image processing apparatus 100 can discharge thesheet S, to which a label is stuck, to the outside of the apparatus. Asa result, the image processing apparatus 100 can suppress the apparatusfrom being broken down because the label R peels in the conveyingmechanism and accumulates on the inside. Further, the image processingapparatus 100 can suppress a paper jam from occurring because of thethickness of the label R.

Note that a part of the functions of the image processing apparatus 100in the embodiments may be realized by a computer. In that case, acomputer program for realizing the functions is recorded in acomputer-readable recording medium. The functions may be realized bycausing the computer system to read the computer program recorded in therecording medium and executing the computer program. Note that the“computer system” includes an operating system and hardware such asperipheral apparatuses. The “computer-readable recording medium” refersto a portable medium, a storage device, or the like. The portable mediumis a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or thelike. The storage device is a hard disk or the like incorporated in thecomputer system. The “computer-readable recording medium” is a recordingmedium that dynamically stores a computer program for a short time likea communication line in transmitting the computer program via acommunication line. The communication line is a network such as theInternet, a telephone line, or the like. The “computer-readablerecording medium” may be a volatile memory inside the computer systemfunctioning as a server or a client. The volatile memory stores acomputer program for a fixed time. The computer-program may be acomputer program for realizing a part of the functions explained above.The computer program may be able to realize the functions in combinationwith a computer program already recorded in the computer system.

According to at least one embodiment explained above, the image readingunit 10 reads the sheet S and generates sheet image data. Thedetermining unit 124 determines, on the basis of a luminance value ofthe sheet image data, whether a label is stuck on the sheet S, which isa reading target. As a result, the image processing apparatus 100 candistinguish a sheet to which an object is stuck and a sheet to which theobject is not stuck.

While certain embodiments have been described these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms: furthermore variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. An image forming apparatus comprising: a feederconfigured to feed a sheet; a conveying unit configured to convey thesheet that has been fed by the feeder; an image forming unit configuredto form an image on the sheet that has been conveyed by the conveyingunit; an image reading unit configured to perform, before the sheet isconveyed to the image forming unit by the conveying unit, a readingoperation for the sheet, which is being conveyed by the conveying unit,to generate sheet image data; a determining unit configured todetermine, on the basis of a degree of gradation in the sheet image datagenerated from the read operation performed by the image reading unit,whether there is a planar object on the sheet read, the planar objectbeing a three-dimensional and tangible object; and a control unitconfigured to control the image forming unit to form an image on theplanar object on the sheet, if the determining unit determines that theplanar object is on the sheet.
 2. The apparatus according to claim 1,further comprising an extracting unit configured to extract, on thebasis of the degree of the gradation, from the sheet image data, an edgeindicating a shadow with respect to thickness of the planar objectprojected on the sheet, wherein the determining unit determines, on thebasis of the edge extracted by the extracting unit, whether the planarobject is on the sheet.
 3. The apparatus according to claim 2, wherein,the determining unit is configured to determine a position of the planarobject on the sheet on the basis of the edge extracted by the extractingunit, if the determining unit determines that the planar object is onthe sheet.
 4. The apparatus according to claim 2, further comprising: aconveying unit configured to convey the sheet; and a conveyance controlunit configured to control, if it is determined that the planar objectis on the sheet, the conveying unit to discharge the sheet to an outsideof the apparatus.
 5. The apparatus according to claim 2, wherein theextracting unit extracts, from the sheet image data, as the edge, atleast any one of a horizontal edge indicating an edge in a horizontaldirection with respect to a conveying direction of the sheet and avertical edge indicating an edge in a vertical direction with respect tothe conveying direction of the sheet.
 6. The apparatus according toclaim 2, wherein the extracting unit converts, for each of pixels, thedegree of the gradation in the sheet image data generated from the readoperation into binary values and, if a predetermined number or more ofpixels that take any one value of the converted binary values arecontinuous, extracts the continuous predetermined number or more ofpixels as the edge.
 7. The apparatus according to claim 2, wherein theextracting unit extracts, on the basis of both of the degree of thegradation of the sheet and a degree of gradation of a background inwhich the sheet is placed, an edge indicating a contour of the sheetread by the reading unit, and the apparatus further comprises acalculating unit configured to calculate, on the basis of conveyingspeed in conveying the sheet read by the reading unit and the edgeindicating the contour of the sheet extracted by the extracting unit, onthe sheet image data, a pixel region indicating a size of the sheet readby the reading unit.
 8. The apparatus according to claim 7, wherein thedetermining unit determines, on the sheet image data, whether an edgeindicating a shadow with respect to thickness of the planar objectprojected on the sheet is included in the pixel region calculated by thecalculating unit and, if the edge indicating the shadow with respect tothe thickness of the planar object is included in the pixel region,determines that the planar object adheres on the sheet.
 9. The apparatusaccording to claim 1, further comprising an irradiating unit configuredto irradiate light to a surface of a sheet, which is a reading target ofthe reading unit, from a predetermined incident angle.